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Discussion Starter · #1 ·
I have a transient noise from the engine compartment. Sometimes it's there, sometimes it's not. It sounds like a bag full of steel poker chips getting flung around on the passenger side of the engine. If you crouch down by the drivers front wheel, you can hear it echoing, and when you crouch down by the passenger front wheel it's loud and annoying... When it happens. Open the hood and it's obviously there, but impossible to pinpoint.

Other days the noise is not there. Only the happy tapping of the lifters and whirring of accessories and the fan. When the noise isn't there, I'd even say it sounds downright pleasant. Sounds newer than it is.

This noise has been with the truck since I bought it 2 years ago. I recently replaced the AC compressor, so I know that's not it, adjusted the valves, had the transmission serviced at the shop that built the transmission and it has a clean bill of health.
It runs great.
The noise does not appear to have any impact on performance at all. I went looking for it with a stethoscope but when I started it up it was just quiet.

The only thing that stands out in my mind is when I went to try and find the noise, it had been sitting for several days with the battery tender plugged in. I try to plug it in if I'm not going to drive it for more than a few days. Would an alternator under load make noise that would not be there all the time? From inside the cab with the windows up I don't hear it.

It's been sitting for a couple days off the charger and I will try again tomorrow to find it, but if anyone recognizes the sound I've described, bag of poker chips getting struck randomly with a steel rod, please let me know.
 

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Welcome to cumminsforum

Disconnect the grid heater relay and drive until you hear the noise again. This will set a CE light while testing.

Do you have the oem air box setup? If so check the air diverter piece in the air tube.

If you hear the noise at night, kill all the lights, pop the hood while its running and look for arcing under the hood. Could be the alternator has an issue. Can check the battery voltages while it is doing it, should be 14.5v or better this time of the year.
 
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Discussion Starter · #3 ·
Welcome to cummins forum
Thanks for the welcome.

Can you give me more details on the grid heater relay disconnect? Reasoning, what to expect, etc.

I do not have a stock air box. It was removed by one of the previous owners. I've recently put a Volant CAI on it in an attempt to quiet it down. It worked really well for that. I couldn't find a stock 05 airbox for a reasonable price and the 06 I bought off CL would not fit. It was close, but I couldn't get it inn there.

Just fyi, this also has an EDGE Juice tuner and CTS2 that came in it when I bought it. I don't beat the truck and keep the power level set to 1. Engine has no blow by and was very well cared for by the POs. I don't think this noise is coming from the block. If it was I would expect it would be just as loud in the drivers side wheel well and be there all the time, but then again, I don't know..

Recently I've been going through the truck in an attempt to "re-civilize" it, from a noise perspective. As I smooth one edge it makes the others sharper. This odd noise is pretty much the last edge.
 

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Ah rghavana has a good point with the belt, also you could put the scope on the alt when you hear it.

On the relay there is a wire going to a terminal, very small wire, remove that and it will disconnect the relay but leave the bigger current draw connected. Without the control wire it should stay open. The thinking is the relay might be oscillating causing your noise. If it is... Check the wiring to it for frayed wires etc...

Another thing to do is turn on the ac and scope the compressor...
 
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The '06 box should be the same as the '05, sure it was not an '07.5?? I think that box is different.

Also if your trying to quiet it down, check the silencer ring on the compressor inlet, if missing get one with snap ring and reinstall it. Guys pull them to listen to the compressor turbulence created when it is gone... Aka turbo whistle. Having it installed puts more into the compressor as it spins.
 
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Discussion Starter · #7 ·
I know it's not the AC compressor. I just had it replace a month ago. The sound it was making was completely different, It had totally failed internally and the bearings in the clutch were gone. It was the first thing I checked when I heard the poker chip noise was still there. I asked them while they were in there to check and replace any tensioners that might be on the way out but he said they were fine. But since this is a come and go kind of thing, who knows.

Raining now, so I may need to wait until tomorrow to test.
 

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Discussion Starter · #8 ·
So I was able to try and test yesterday. No noise, so I'm still looking.
However, the noise itself has been bothering me because it's a noise I recognized but couldn't pin down. I don't know if I'm getting Alzheimer's or just working too much but I finally remembered what that poker chip noise is. At least in gas vehicles, It's the sound of pre-detonation/valves.
I'm not certain that what I've been hearing is actually valves, but it has that same valve vibrating to a stop sound you would get from a gas motor experiencing run on, but without the knocking. Not sure why my brain thought poker chips and not valves. I don't play poker, but I do play with cars.
Maybe this is just a fuel quality issue. Or too much Diesel Kleen. On my last fill up I didn't add any Diesel Kleen, because I'd put the max recommended amount in prior. Maybe this was just dirty injectors, or the Edge set to wrong power level.

I'm going to keep my stethoscope in the truck so if it ever comes back, I can track it down. If I do, I'll follow up to this post.
 

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Do you hear it at an idle or only under load?

If you use an additive that reduces the ignition delay in cylinder then you can get timing rattle. Take some mental notes as to when you hear it and under what conditions. RPMs, load, ambient temps etc.

Consider trying the ATF/2SO mix outlined in the Newbies Guide thread, if there is carbon buildup on the pistons, even one or two of them, it will shorten the ignition delay and could cause timing rattle. Maybe even at idle, although I have not heard of that one yet there could be a 1st... If you do the ATF/2SO mix give it 300ish miles to do its thing. Also consider using a stiction eliminator in the oil such as Hot Shots Secret stiction eliminator. Since my truck has been on the mix and the SE it has run extremely well over the longest time period... at this time its 150k or so miles, since the last injector install. It has never run this well this long and I point to those 2 changes... the mix & the SE.
 
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